This invention relates to a cooling system for an electronic apparatus, and more particularly to a liquid cooling system wherein each circuit module is cooled with a liquid via a cold plate or cooling chamber, and a handling method thereof.
A multichip module comprising a number of high density LSIs mounted on a relatively small circuit board generates a large amount of heat per unit area. Accordingly, a liquid cooling system is often employed wherein each module is cooled with a liquid via a cold plate or cooling chamber. Examples of this type of cooling system are disclosed in U.S. Pat. No. 3,481,393 of Richard C. Chu, issued on Dec. 2, 1969, and in "Liquid-cooling Multichip Packages" by Murano et al., NIKKEI ELECTRONICS, 1985.6.17, pp.243-266.
In such a liquid cooling system a cold plate or cooling chamber is attached to each multichip module such that one side of the cold plate is in tight contact with the multichip module to obtain high heat conductivity. The cold plate has a coolant path provided therein, and a plurality of cold plates are connected in series by flexible hoses or conduits to form a string of cold plates. A plurality of such strings are connected in parallel between the supply duct and the return duct of a coolant circulating system.
As explained in the above-mentioned U.S. patent, the prior art liquid cooling systems attach importance to ease with which any cold plate or cooling chamber can be detached from its associated multichip module with hoses being kept connected thereto. This feature is advantageous in that any module can be serviced or replaced without stopping the coolant circulation, that is, without affecting the cooling of other modules.
As the amount of heat generated by each multichip module increases, improvement in cooling efficiency is required. Thus it is desired to reduce the heat resistance between the multichip module and the cold plate or cooling chamber as much as possible. In order to achieve this, the contact condition of the cold plate to the multichip module must be carefully adjusted so that the best condition may be realized. It is usual to apply a heat conductive grease or compound onto both of the facing contacting surfaces in order to decrease the heat resistance.
Under those circumstances the detaching of the cold plate from the multichip module for maintenance or service produces problems. When a cold plate, once detached from a multichip module, is to be attached again to the same or a new multichip module, the above-described careful adjustment of the contact condition or the wiping off and reapplication of the grease is necessary. Unfortunately, it is difficult at the spot where the machine is in use to achieve the delicate adjustment of the contact condition owing to poor facilities. Also, the removal and reapplication of the grease take a considerable length of time, during which the system is left unavailable, and the use of the grease must be given up if the circumstances are unfavorable.